RICHMOND -- After forming an alliance to conquer Chevron and its millions in campaign spending in last year's election, Mayor Tom Butt and the political progressives on the City Council have increasingly turned their fire on one another.

Hopes for a new era of City Council harmony have quickly vanished amid a fusillade of verbal blows -- most notably over the issue of rent control -- traded at meetings and in social media between Butt and members of the Richmond Progressive Alliance, who hold three of the council's seven seats.

The issue that united Butt and the progressives last November -- their stand against the influence of Big Oil in the city -- has faded, replaced by bitter divisions over the role of space-based weapons, the location of a historic World War II cargo ship and whether Richmond should become the first California city in three decades to impose rent control.

Butt has repeatedly taken to his popular online forum to attack the RPA, accusing it of trying to impose its will through heavy-handed tactics.

"When the RPA came to town, they set themselves up as the antidote to corruption and old-style power politics in Richmond," he wrote. "But power has been seductive, and the RPA has taken on many of the trappings of the power politics they once eschewed."

RPA members have been equally blunt in their criticism of the new mayor.

"The mayor has basically declared war on RPA in his e-forum," said Jovanka Beckles, one of the progressives who surged to victory in November. "Every opportunity he has, he throws in something to put down the organization, something to discredit us. We don't want a war with him, but at the same time, we can't stand by and watch the lies he says without defending ourselves."

Butt and Councilwoman Gayle McLaughlin, his predecessor as mayor, downplay the dissension and note that the new council majority has found common ground on a number of issues. But many agree that the political rhetoric has grown increasingly tense and occasionally downright nasty in recent months.

"The RPA doesn't compromise on a general basis, and Tom can be very obstinate and hold a grudge," said Don Gosney, a Richmond resident who follows the City Council closely. "Ultimately, it's the people who lose out when so much of our meetings are tied up with infighting."

The RPA played a key role in Butt's election victory last year when it opted to back the longtime councilman rather than put up one of its own members for mayor. Butt, who like the RPA is a longtime critic of Chevron's Richmond refinery, threw his support behind the RPA's "Team Richmond" slate, including two-term mayor McLaughlin, for three open council seats.

More than $3 million in spending by Chevron went up in smoke when Butt and the progressives trounced the company's preferred candidates.

But observers say the alliance almost immediately began to fray when the new council sought to fill a vacant seat created by Butt's mayoral election. The progressive faction favored appointing one of its own members -- which would give them a majority on the council --while the mayor and Councilman Jael Myrick wanted someone more neutral, which they got in eventual appointee Vinay Pimplé.

In May, they clashed again over a resolution that sought to declare Richmond free from technologies such as particle beams, electromagnetic radiation and ultra high-frequency energy radiation.

The item, supported by all council members besides Butt and Pimplé, received national attention and plenty of scorn after hundreds of "targeted individuals" began contacting Richmond police with requests to investigate.

"The victory in 2014 emboldened the RPA to move into more aggressive areas, such as the space weapons issue," said Butt in an interview last week. "It cost them a lot of credibility and left a lot of people -- both in and outside of Richmond -- shaking their heads."

That was followed by a fight over the best place to move a World War II-era cargo ship after a winery complained that it was blocking its views. The progressives accused Butt of acting like a bully when he didn't get his way.

But tensions reached their apex in late July as the council sparred over a hotly debated rent control ordinance. When Butt voted against continuing a meeting so that a vote could take place, the RPA council members hastily called two special meetings, further aggravating the mayor, who said there were now "two parallel city councils in Richmond."

The mayor then posted a fiery letter on his e-forum in which he accused the RPA of strong-arming meetings in violation of the Brown Act, which ensures transparency in local government.

McLaughlin said rent control supporters acted legally and called a special meeting to finish an important piece of business before the council's summer break. She disputed the mayor's portrayal of the RPA as a secret and powerful group and said it was in the process of reorganizing to attract new members.

"The real power in Richmond is still the large corporations, developers and real estate interests with more than enough money to pollute our politics as we have seen with the petition (to resind rent control)," McLaughlin said in an email.

And while rent control is expected to continue to dominate city politics for months to come, the tensions between the two camps have raised questions about how the toxic rhetoric impacts the group's ability to work together.

Both Butt and McLaughlin insist there is no great schism and say there are many issues on which they see eye to eye.

"I'm always happy to compromise with Tom on issues of which we have basic agreement, and many such compromises have occurred already this year," McLaughlin said.

The mayor is also eager to downplay any tensions: "I'm hopeful that these things will fall by the wayside and am optimistic that it will be OK. But I do hope that it will be OK sooner rather than later."

Beckles, though, worries that if the divide continues, the real winner could ultimately be the biggest loser from last November.

"The only people who are going to win from a divisive council are big money; it's corporations like Chevron," she said.